According to Bob May :
I thought all of the carbon/zinc type batteries had negative cases.

Most did -- but the zinc/carbon individual cells are relatively
rare now. An example of the zinc-carbon ones without a negative case
are the ones which were used to make high voltage batteries (even the 9V
ones) were a wax ring (shaped sort of like a tire) with a zinc plate at
one end and carbon at the other, with the sal-ammoniac (IIRC) in
between. All of the wax rings were joined end to end by melting the
wax, and this connected all the cells in series.

The
little button on the top is the positive contact for the battery and the
other end is essentially flat on most batteries today with some having a
stamped bottom and sides in contact.

The "little button on the top" was a metal cap over the end of
the central carbon rod which was the actual positive terminal.

However, the Alkaline cells use a different chemistry (I'm not
sure of the details -- but it could be looked up), and the positive
terminal makes the case -- which requires a strange form factor to deal
with all the equipment designed to orient the button properly as a
positive terminal. A standard flashlight would not care, but most
electronic stuff powered by batteries does care, which is why they
continue to shape things so the button is positive, even if it is
connected to the case. The common coin cells are different, because
there were never any of those with the button as positive.

Enjoy,
DoN.
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